Conventional buck converters are often controlled by comparison of inductive energize time with a voltage error term. Inductive energize time is often represented by a ramp signal. An auxiliary feedback loop based on current mode control is sometimes used in conjunction with voltage control to improve performance during continuous conduction mode (CCM). There are many prior art “slope compensation” techniques that modify the slope of the ramp signal to improve the stability of the converter control loop and/or to improve its dynamic response. Such techniques are effective to the extent that they approximate the underlying equations relating energy to voltage and current, which formulas for energy transfer relate to the squares of the voltages and currents involved. To the extent that prior art techniques fail to conform to the underlying energy equations, they fail to optimize regulation dynamics and flexibility.
When the voltage error term in a conventional power converter is too small, or too delayed, to provide adequate and timely feedback, its control loop is effectively opened and instability results. Conventional converters are often only stable over a restricted range of duty cycles. Once the feedback loop is opened, or an element of positive feedback is introduced, poor transient response, oscillation or even a destructive runaway condition may result.
Additionally, even with per-cycle energy balancing, recovery from severe transients may suffer if energy balance information is destroyed at the beginning of each chopping cycle.